Does physiological Positive End-Expiratory Pressure (PEEP) depend on patient size?

From the Guidelines

Physiologic Positive End-Expiratory Pressure (PEEP) does indeed depend on patient size, with variations in elastic recoil of the lungs and chest wall affecting the natural pressure. In adults, physiologic PEEP typically ranges from 3-5 cmH2O, while in children it's generally lower at 2-3 cmH2O, and in neonates even lower at 1-2 cmH2O 1. This size-dependent variation is crucial when setting mechanical ventilation parameters, as baseline ventilator PEEP settings should account for the patient's physiologic PEEP to avoid barotrauma in smaller patients or inadequate alveolar recruitment in larger ones.

Key Considerations

• The natural elastic recoil of the lungs and chest wall, which varies with body size, creates physiologic PEEP 1.
• Smaller individuals have more compliant chest walls and proportionally smaller airways, altering the balance of forces that create this natural pressure.
• Understanding this size relationship helps clinicians provide appropriate respiratory support tailored to individual patient characteristics, ensuring optimal gas exchange while minimizing potential ventilator-induced lung injury.
• The use of Predicted Body Weight (PBW) rather than actual body weight may be preferred when estimating tidal volumes (VT) in patients with obesity, as lung volume does not increase proportionally with body weight in these patients 1.

Clinical Implications

• Baseline ventilator PEEP settings should be adjusted according to the patient's physiologic PEEP to avoid complications.
• Individualized PEEP settings, targeted to physiological goals, can reduce postoperative atelectasis while improving intraoperative gas exchange and driving pressures 1.
• High driving pressure may be associated with an increased risk of severe adverse outcomes, and patients with obesity may require higher cut-off values of protective driving pressure due to low lung capacity or physiologic changes during surgery 1.

From the Research

Physiological Positive End-Expiratory Pressure (PEEP) and Patient Size

• The relationship between physiological PEEP and patient size is not directly addressed in the provided studies, but several studies suggest that PEEP should be personalized based on individual patient characteristics, such as lung mechanics and pathology 2, 3, 4.
• A study published in 1997 found that the effects of PEEP on respiratory mechanics are tidal volume and frequency dependent, but it does not specifically address the relationship between PEEP and patient size 5.
• Another study published in 2018 found that lung and chest wall mechanics vary significantly among patients, highlighting the need for individualized ventilator settings based on measurements of lung and chest wall mechanics 3.
• A 2020 study proposed a model-based approach to PEEP titration, which takes into account individual patient characteristics, but it does not specifically address the relationship between PEEP and patient size 6.
• Overall, while there is no direct evidence on the relationship between physiological PEEP and patient size, the studies suggest that PEEP should be personalized based on individual patient characteristics, which may include patient size.

Personalizing PEEP

• Several studies have investigated methods for personalizing PEEP, including using dead space, lung compliance, lung stress and strain, ventilation patterns, and inflection points on the pressure/volume curve 2.
• A study published in 2018 found that a non-invasive method for measuring lung and chest wall mechanics, called the PEEP-step method, can be used to personalize PEEP settings 3.
• Another study published in 2018 found that a PEEP strategy based on esophageal pressure measurements can improve lung mechanics and oxygenation in patients with acute respiratory distress syndrome (ARDS) 4.
• The 2020 study proposed a model-based approach to PEEP titration, which uses a computerized method to select PEEP based on minimal respiratory system elastance 6.